Solar receiver with direct absorption media irradiation

ABSTRACT

A solar receiver having a receiver vessel with a receiver chamber, a receiver cover with a receiver window, a receiver fluid inlet, a receiver fluid outlet, and an absorption media matrix in the receiver chamber. In operation of the solar receiver, incident solar radiation is transmitted through the receiver window to the absorption media matrix. Receiver fluid is circulated through the receiver chamber and the absorption media matrix. Heat is transferred from the absorption media matrix to the receiver fluid.

BACKGROUND

This invention is in the field of devices and methods for solar energy collection and in particular in the field of devices and methods for the reception and absorption of solar radiation by an absorption media and transfer of the energy of the absorbed solar radiation to a transfer fluid.

There are many prior art devices and methods for the reception and absorption of solar radiation. These prior art devices may provide for the reception and absorption of radiation directly from the sun, or may provide for the reception and absorption of concentrated solar radiation from a solar collector, or both. The received and absorbed radiation may result in the direct generation of electric current, as for a photovoltaic system, or the absorbed solar energy may be transferred to a heat transfer fluid. These prior art devices involve varying levels of initial cost, operation and maintenance cost, operational complexity, operational reliability and efficiency.

It is an objective of the present invention to provide a solar receiver and a method for solar reception and absorption with low initial cost, low operation and maintenance cost, low operational complexity, long operational lifetime, and moderate to high efficiency.

It is a further objective of the present invention to provide a solar receiver and a method for solar reception and absorption that may be used for direct solar irradiation or may be used with concentrated solar radiation from a solar collector.

It is a further objective of the present invention to provide a solar receiver and a method for solar reception and absorption that may provide for the direct irradiation of a solar absorption media which is contained in and enveloped by a receiver fluid.

SUMMARY OF THE INVENTION

The solar receiver of the present invention is comprised of a receiver vessel with a receiver chamber and a receiver cover with a receiver window, a chamber inlet, a chamber outlet, and an absorption media matrix in the receiver chamber. For an operation of the solar receiver, receiver fluid is circulated through the receiver chamber. The solar receiver may also incorporate chamber baffles which reduce short circuiting of the receiver fluid as it flows through the receiver chamber.

For a preferred embodiment of the solar receiver, the receiver fluid will preferably be air or other low density gas, such as nitrogen or an inert gas, as to increase the transmissivity of the incident solar radiation to the absorption media of the absorption media matrix. However, other embodiments may utilize clear, high transmissivity liquids, such as water, alcohol, molten salt, or light oils. The receiver vessel may have a receiver cover with a receiver window. The receiver cover may be attached to the receiver vessel wall by cover hinges, secured by a cover latch, and sealed against leakage of the receiver fluid from the receiver chamber by a fluid seal between the receiver chamber top and the receiver cover. This embodiment of the solar receiver works particularly well for use with a low pressure gas, such as low pressure air, for a receiver fluid.

A preferred material to be used for the absorption media of the absorption media matrix is a copper wool, a copper-aluminum alloy wool, or other metallic wool having a high thermal absorption rate and a high thermal conductivity. The thermal absorption rate of absorption media may be enhanced by a surface treatment, such as anodization that can be used for a copper-aluminum alloy. For preferred embodiments, the configuration of the absorption media matrix and the characteristics of the absorption media, such as fiber diameter and the total length of fiber per unit volume of absorption media for absorption media in the form of a wool-like fiber matrix, will be selected to provide for the penetration to matrix internal positions, and, therefore, for depth distribution in the absorption media matrix of the incident solar radiation transmitted to the receiver chamber by the receiver window, thereby providing for a more uniform distribution through the absorption media matrix of the energy absorbed from the incident solar radiation. The use of a high thermal conductivity material for the absorption media, such as copper wool, will result in the rapid redistribution of the absorbed energy, which will, in turn, aid in the transfer of the solar energy absorbed by the absorption media matrix to the receiver fluid.

The receiver fluid, which will preferably be a low density compressible fluid, such as air at a pressure only slightly above ambient air pressure, is introduced at a chamber inlet and follows a chamber fluid path through the receiver chamber with chamber baffles minimizing short circuiting of the chamber fluid path. Solar energy absorbed and distributed by the absorption media matrix, which, for preferred embodiments, may fill the receiver chamber, is transferred to the receiver fluid. The heated receiver fluid exits the receiver chamber through the chamber outlet to the discharge conduit which conveys the heated receiver fluid to equipment or devices for further heat exchange or utilization of the energy, such as driving a steam turbine, or other beneficial use of the received solar energy, which uses and applications will be known to persons skilled in the art.

For a preferred embodiment, the receiver window may be a material such as glass or plastic which has a low reflectivity for the incident solar radiation, preferably for a spectrum including high infrared, visible light, and low ultraviolet, regardless of the radiation incidence angle of the solar radiation. In the interest of maximizing the transmission of the incident solar radiation to the absorption media matrix, a course fiber matrix may be preferable for the absorption media of the absorption media matrix. Despite the preferred high thermal conductivity for the absorption media, the better the distribution of the incident solar radiation to the absorption media, the more efficient the energy transfer to the receiver fluid will be as the receiver fluid flow through the receiver chamber and the absorption media matrix occurs. As noted above, a preferred material for the absorption media is a copper wool or other metallic wool, which may have an absorption enhancing surface to darken the surface of the absorption media thereby increasing the rate of absorption and decreasing the rate of reflection of the incident solar radiation from the surface of the absorption media. The receiver window may have a reflective undercoating which will reduce the radiative loss of reflected chamber radiation and the infrared radiative loss of emitted infrared radiation.

A preferred embodiment of the solar receiver of the present invention has a receiver chamber with a horizontal rectangular cross-section and a vertical rectangular cross section. However, other configuration shapes of the receiver vessel and the receiver chamber will be obvious to persons with skill in the art in view of the disclosures made in the specification and the drawings of this application. A receiver chamber containing an absorption media matrix of absorption media and having a receiver cover with a receiver window providing for the transmission of the incident solar radiation to the receiver chamber and for the direct irradiation of the absorption media of the absorption media matrix of high thermal conductivity absorption media material, and providing for the circulation of receiver fluid through the receiver chamber and the absorption media matrix are the principal components of the preferred embodiment of the present invention. The receiver cover may provide for the cleaning, servicing, removal and replacement of the absorption media and the absorption media matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view perspective of a preferred embodiment of the solar receiver of the present invention.

FIG. 2 is a plan view, horizontal cross-section of a preferred embodiment of the solar receiver of the present invention with chamber baffles.

FIG. 3 is a side view, vertical cross-section of a preferred embodiment of the solar receiver of the present invention with chamber baffles.

FIG. 4 is a side view perspective of an alternative preferred embodiment of the solar receiver of the present invention having a cylindrical receiver vessel with a cylindrical receiver chamber.

FIG. 5 is a flow schematic of a parallel receiver network incorporating a plurality of the solar receivers of the present invention connected in parallel.

FIG. 6 is a flow schematic of a series receiver network incorporating a plurality of the solar receivers of the present invention connected in series.

FIG. 7 is a plan view, horizontal cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a central chamber receiver fluid outlet.

FIG. 8 is a plan view, horizontal cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a central chamber receiver fluid inlet.

FIG. 9 is a plan view, horizontal cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a spiral flow path and a central chamber receiver fluid outlet.

FIG. 10 is a plan view, horizontal cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a spiral flow path and a central chamber receiver fluid inlet.

FIG. 11 is a side view, vertical cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a central chamber receiver fluid outlet.

FIG. 12 is a side view, vertical cross-section of an alternative preferred embodiment of the solar receiver of the present invention with a central chamber receiver fluid inlet.

DETAILED DESCRIPTION

Referring first to FIG. 1, a side view perspective of a preferred embodiment of the solar receiver 1 of the present invention is shown. Referring also to FIG. 2, a horizontal cross-section is shown of the preferred embodiment of the solar receiver 1 shown in FIG. 1. For the embodiment shown, the solar receiver 1 is comprised of a receiver vessel 3 with a receiver chamber 4 and a receiver cover 5 with a receiver window 6, a chamber inlet 7, a chamber outlet 9, and an absorption media matrix 11 in the receiver chamber 4. For an operation of the solar receiver 1, receiver fluid 13 is circulated through the receiver chamber 4. The embodiment of the solar receiver 1 shown in FIG. 1 and FIG. 2 may also incorporate chamber baffles 15 as shown in FIG. 2 and FIG. 3, which reduce short circuiting of the receiver fluid 13 as it flows through the receiver chamber 4.

For the preferred embodiment of the solar receiver 1 shown in FIG. 1 and FIG. 2, the receiver fluid 13 may be air or other low density gas, such as nitrogen or an inert gas, so as to increase the transmissivity of the incident solar radiation 19 to the absorption media 21 of the absorption media matrix 11. However, other embodiments may utilize clear, high transmissivity liquids, such as water, alcohol, molten salt, or light oils. For the embodiment shown in FIG. 1 and FIG. 2, the receiver vessel 3 may have a receiver cover 5 with a receiver window 6. The receiver cover 5 may be attached to the receiver vessel wall 25 by cover hinges 27, secured by a cover latch 28, and sealed against leakage of the receiver fluid 13 from the receiver chamber 4 by a fluid seal 29 between the receiver chamber top 31 and the receiver cover 5.

A preferred material to be used for the absorption media 21 of the absorption media matrix 11 is a copper wool, a copper-aluminum alloy wool, or other metallic wool having a high thermal absorption rate and a high thermal conductivity. The thermal absorption rate of absorption media 21 may be enhanced by a surface treatment, such as anodization that can be used for a copper-aluminum alloy. For preferred embodiments, the configuration of the absorption media matrix 11 and the characteristics of the absorption media 21, such as fiber diameter and the total length of fiber per unit volume of absorption media 21 for absorption media 21 in the form of a wool-like fiber matrix, may be selected to provide for the penetration of the incident solar radiation 19 to matrix internal positions 20 as shown also on FIG. 3. This may be accomplished by providing a unobstructed ray path, for the incident solar radiation 19 transmitted through the receiver window 6, from the receiver window 6 to the matrix internal positions 20. The absorption media 21 and the transmissivity of the receiver fluid 13 provide, for preferred embodiments, for depth distribution in the absorption media matrix 11 of the incident solar radiation 19 transmitted to the receiver chamber 4 by the receiver window 6, thereby providing for a more uniform distribution through the absorption media matrix 11 of the energy absorbed from the incident solar radiation 19. The use of a high thermal conductivity material for the absorption media 21, such as copper wool, will result in the rapid redistribution of the absorbed energy which will in turn aid in the transfer of the solar energy absorbed by the absorption media matrix 11 to the receiver fluid 13. Alternative embodiments may incorporate a denser configuration of absorption media 21 and provide for absorption of most of the incident solar radiation 19 by the absorption media 21 at or near the top of the absorption media matrix 11. These alternative embodiments may depend on a high thermal conductivity of the absorption media 21 to provide for the rapid distribution of the absorbed energy.

For the embodiment of the solar receiver shown in FIG. 1 and FIG. 2, receiver fluid 13, which may be a low density compressible fluid, such as air at a pressure only slightly above ambient air pressure, is introduced at the chamber inlet 7 and follows a chamber fluid path 33 through the receiver chamber 4 with the chamber baffles 15 minimizing short circuiting of the chamber fluid path 33. Solar energy absorbed and distributed by the absorption media matrix 11 which, for preferred embodiments, may fill the receiver chamber 4, is transferred to the receiver fluid 13. The heated receiver fluid 35 exits the receiver chamber 4 through the chamber outlet 9 to the discharge conduit 10 which conveys the heated receiver fluid 35 to equipment or devices for further heat exchange or utilization of the energy, such as driving a steam turbine, or other beneficial use of the received solar energy, which uses and applications will be known to persons skilled in the art.

Referring now also to FIG. 3, a vertical cross section of the preferred embodiment of the solar receiver 1 illustrated and depicted in FIG. 1 and FIG. 2, is shown. For a preferred embodiment, the receiver window 6 may be a clear, transparent material, such as glass or plastic, which will have a low reflectivity for the incident solar radiation, preferably for a spectrum including high infrared, visible light, and low ultraviolet, regardless of the radiation incidence angle 37 of the solar radiation 19 as shown in FIG. 1. In the interest of maximizing the transmission of the incident solar radiation 19 to the absorption media matrix 11, a course fiber matrix may be preferable for the absorption media 21 of the absorption media matrix 11. Despite the preferred high thermal conductivity for the absorption media 21, the better the distribution of the incident solar radiation to the absorption media 21, the more efficient the energy transfer to the receiver fluid 13 will be as the receiver fluid flow 43 through the receiver chamber 4 and the absorption media matrix 11 occurs. As noted above, a preferred material for the absorption media 21 is a copper wool or other metallic wool, which may have an absorption enhancing surface to darken the surface of the absorption media 21 thereby increasing the rate of absorption and decreasing the rate of reflection of the incident solar radiation from the surface of the absorption media 21.

Referring further to FIG. 3, the receiver window 6 may have a reflective undercoating 47 which will reduce the radiative loss 49 and increase the internal reflection retention 54 of reflected chamber radiation 51, and will reduce the infrared radiative loss 52 and increase the internal infrared reflection retention 56 of emitted infrared radiation 53. Various materials and designs for the receiver window 6 will be known to persons of ordinary skill in the art for minimizing the reflectivity and maximizing the transmissivity of the incident solar radiation 19 while at the same time maximizing the reflectivity and minimizing the transmissivity of the radiation reflected from or emitted from the absorption media 21 or the receiver fluid 13.

Referring further to FIG. 3, the receiver chamber walls 55 and the receiver chamber bottom 57 may be equipped with a chamber insulation layer 59 and a wall reflective surface 61 which may reduce the convective and radiative losses of heat through the chamber walls 55 or chamber bottom 57.

A preferred embodiment of the solar receiver 1 of the present invention, as shown in FIG. 1, FIG. 2 and FIG. 3 has a box shaped receiver chamber 4 with a horizontal rectangular cross-section as shown in FIG. 2, and a vertical rectangular cross section as shown in FIG. 3. However, other configuration shapes of the receiver vessel 3 and the receiver chamber 4 will be obvious to persons with skill in the art in view of the disclosures made in the specification and the drawings of this application. A receiver chamber 4 containing an absorption media matrix 11 of absorption media 21 and having a receiver cover 5 with a receiver window 6 providing for the transmission of the incident solar radiation to the receiver chamber 4 and for the direct irradiation of the absorption media 21 of the absorption media matrix 11 of high thermal conductivity absorption media material, and providing for the circulation of receiver fluid through the receiver chamber 4 and the absorption media matrix 11 are the principal components of the preferred embodiment of the present invention which is illustrated in FIG. 1, FIG. 2 and FIG. 3. The receiver cover 5 as shown in FIG. 1 may provide for the cleaning, servicing, removal and replacement of the absorption media 21 and the absorption media matrix 11.

As indicated above, the embodiment of the solar receiver 1 shown in FIG. 1 and FIG. 2 is particularly well suited for use with a low pressure gas, such as air at a pressure only slightly above ambient pressure, for a receiver fluid 13. However, this embodiment is also well suited for use with a low pressure liquid, such as water, for a receiver fluid 13. Such an embodiment may be used for a domestic or commercial water heater for heating water to be used directly in a residence or business. Such an embodiment may be combined with a pumping system to provide pressure for hot water usage. Such an embodiment may also be used to supply heat to a heat exchanger that transfers heat to a pressurized water system.

Alternative embodiments of the receiver vessel 3, particularly embodiments for using air or other gas for the receiver fluid 13, may provide for access to the receiver vessel to be provided by a side, end or bottom access, with a fluid seal to prevent receiver fluid 13 leakage. For such embodiments, the receiver window 6 may be incorporated in the receiver vessel top 8 and not incorporated in a receiver chamber top access 12 shown in FIG. 1.

An alternative preferred embodiment of the solar receiver 1 of the present invention is shown in FIG. 4. This embodiment of the solar receiver 1 has a cylindrical receiver vessel 3 with a cylindrical receiver chamber 4. For this embodiment the receiver window 6, may be curvilinear as shown in FIG. 4, which may provide for an improved efficiency if the solar receiver 1 is not integrated with a solar tracking mechanism. By contrast, the embodiment of the solar receiver shown in FIG. 1, FIG. 2 and FIG. 3 will have a reduced efficiency during the early morning hours and late afternoon hours unless the solar receiver 1 is integrated with a solar tracking mechanism. This cylindrical shaped alternative embodiment may be more easily adapted to use with a high pressure receiver fluid 13. This alternative embodiment may also have a receiver chamber constructed entirely of glass or other high transmissivity or transparent material. This alternative may increase the efficiency of the radiation absorption, while taking advantage of the low transmissivity rate of glass and other transparent material for longer wavelength infrared, thereby reducing radiative losses.

Embodiments of the solar receiver 1 of the present invention may be used for direct solar irradiation or may be used for concentrated solar radiation from a solar collector. For embodiments used for concentrated solar radiation, attention must be directed to distributing the concentrated radiation over the receiver window 6, selection of material for the absorption media 21, selection of the receiver fluid 13, and providing for a receiver fluid circulation capacity that is compatible with the concentrated radiation intensity and daily and seasonal variations of the radiation intensity. The term “incident solar radiation” as used in this specification, including the claims, shall be defined to include both direct solar radiation and concentrated solar radiation.

Referring now to FIG. 5, it should be noted that the solar receiver 1 of FIG. 1 and FIG. 2, as well as alternative embodiments, may be used alone or in conjunction with other solar receivers 1 of similar design. The solar receivers 1 may be connected in parallel, for a parallel receiver network 71 as shown in FIG. 5, or in series, for a series receiver network 81, as shown in FIG. 6. However, it should be noted that the series receiver network 81 embodiment shown in FIG. 6 may result in a reduced overall efficiency as the increasing temperature of the heated receiver fluid 35 may result in a decrease in the energy heat transfer rate from the absorption media 21 of the absorption media matrix 11 as the temperature differential between the heated receiver fluid 35 and the absorption media 21 decreases.

Referring now to FIG. 7, an alternative embodiment of the solar receiver 1 and the receiver vessel 3 is shown. For the embodiment shown, the receiver vessel 3 has a box shaped receiver chamber 4 and has a generally rectangular vessel perimeter 79, a peripheral chamber receiver fluid inlet 83, and a continuous chamber baffle 71 which directs the receiver fluid 13 through the absorption media 21 of the absorption media matrix 11 in a generally rectangular chamber fluid path 75. Referring also to FIG. 11, heated receiver fluid 35 exits the receiver chamber 4 through a central chamber receiver fluid outlet 67 in the chamber bottom 57.

Referring now to FIG. 9, a further alternative embodiment of the solar receiver 1 and the receiver vessel 3 is shown. For the embodiment shown, the receiver vessel 3 has a generally spiral vessel perimeter 81, a peripheral chamber receiver fluid inlet 83, and a continuous generally spiral chamber baffle 73 which directs the receiver fluid 13 through the absorption media 21 of the absorption media matrix 11 in a generally spiral chamber fluid path 77 which may have a rectangular cross section. Referring also to FIG. 11, heated receiver fluid 35 exits the receiver chamber 4 through a central chamber receiver fluid outlet 67 in the chamber bottom 57.

Referring now to FIG. 8, a further alternative embodiment of the solar receiver 1 and the receiver vessel 3 is shown. Referring also to FIG. 12, for the embodiment shown, the receiver vessel 3 has a box shaped receiver chamber 4 and has a generally rectangular vessel perimeter 79, a central chamber receiver fluid inlet 69 in the chamber bottom 57 where the receiver fluid 13 flows into the receiver chamber 4, and a continuous chamber baffle 71 which directs the receiver fluid 13 through the absorption media 21 of the absorption media matrix 11 in a generally rectangular chamber fluid path 75. Heated receiver fluid 35 exits the receiver chamber 4 through a peripheral chamber receiver fluid outlet 85.

Referring now to FIG. 10, a further alternative embodiment of the solar receiver 1 and the receiver vessel 3 is shown. Referring also to FIG. 12, for the embodiment shown, the receiver vessel 3 has a generally spiral vessel perimeter 81, a central chamber receiver fluid inlet 69 in the chamber bottom 57 where the receiver fluid 13 flows into the receiver chamber 4, and a continuous spiral chamber baffle 73 which directs the receiver fluid 13 through a generally spiral chamber fluid path 77 which may have a rectangular cross section. Heated receiver fluid 35 exits the receiver chamber 4 through a peripheral chamber receiver fluid outlet 85.

In view of the disclosures of this specification and the drawings, other embodiments and other variations and modifications of the embodiments described above will be obvious to a person skilled in the art. Therefore, the foregoing is intended to be merely illustrative of the invention and the invention is limited only by the following claims and the doctrine of equivalents. 

What is claimed is:
 1. A solar receiver for receiving and absorbing incident solar radiation and transferring energy received and absorbed from the incident solar radiation to a receiver fluid, the solar receiver comprising: a receiver vessel having a receiver chamber, a receiver fluid inlet, a receiver fluid outlet, and a receiver window; and an absorption media matrix positioned in the receiver chamber, the absorption media matrix being comprised of absorption media.
 2. The solar receiver recited in claim 1 wherein the absorption media matrix has physical characteristics providing for penetration of a portion of the incident solar radiation transmitted by the receiver window to the receiver chamber, to positions internal to the absorption media matrix.
 3. The solar receiver recited in claim 1 wherein the absorption media comprises a fiber matrix of fibers having a fiber diameter and a total length of fiber per unit volume of absorption media which provide for penetration of a portion of the incident solar radiation transmitted by the receiver window to the receiver chamber, to positions internal to the absorption media matrix.
 4. The solar receiver recited in claim 1 wherein the receiver chamber is box shaped.
 5. The solar receiver recited in claim 1 wherein the receiver chamber is spiral shaped.
 6. The solar receiver recited in claim 1 wherein the receiver chamber is cylindrically shaped and has a curvilinear receiver window.
 7. The solar receiver recited in claim 1 wherein the receiver chamber has one or more chamber baffles.
 8. The solar receiver recited in claim 1 wherein the receiver chamber has one or more chamber baffles for reducing short circuiting of receiver fluid as it follows a chamber fluid path through the receiver chamber from the receiver fluid inlet to the receiver fluid outlet.
 9. The solar receiver recited in claim 1 wherein the receiver window has a reflective undercoating for reducing a radiative loss of reflected chamber radiation and a radiative loss of infrared radiation emitted from the receiver chamber.
 10. The solar receiver recited in claim 1 wherein the receiver vessel has a receiver door with a receiver door fluid seal.
 11. The solar receiver recited in claim 1 wherein the absorption media is a metallic wool.
 12. A method for receiving and absorbing incident solar radiation and transferring energy received and absorbed from the incident solar radiation to a receiver fluid, the method comprising: providing a solar receiver having a receiver vessel with a receiver window, a receiver chamber, a receiver fluid inlet, and a receiver fluid outlet, the receiver chamber having an absorption media matrix of absorption media; transmitting the receiver fluid through the receiver fluid inlet to the receiver chamber; irradiating the receiver window with the incident solar radiation, the receiver window transmitting a first portion of the incident solar radiation to the receiver chamber; transmitting a second portion of the first portion of the incident solar radiation through the receiver fluid directly to the absorption media of the absorption media matrix, the receiver fluid having a transmissivity which provides for the transmission of the second portion of the first portion of the incident solar radiation directly to the absorption media of the absorption media matrix without being absorbed by the receiver fluid; passing the receiver fluid through the absorption media of the absorption media matrix and transferring heat from the absorption media to the receiver fluid, producing heated receiver fluid; and transmitting the heated receiver fluid from the receiver chamber through the receiver fluid outlet.
 13. The method recited in claim 12 wherein the absorption media provides for penetration of the second portion of the first portion the incident solar radiation to positions internal to the absorption media matrix.
 14. The method recited in claim 12 wherein the absorption media is comprised of a fiber matrix of fibers having a fiber diameter and a total length of fiber per unit volume of absorption media which provide for penetration of the second portion of the first portion of the incident solar radiation to positions internal to the absorption media matrix.
 15. The method recited in claim 12 wherein the receiver window has a reflective undercoating for reducing a radiative loss of reflected chamber radiation and a radiative loss of infrared radiation emitted from the receiver chamber.
 16. The method recited in claim 12 wherein the receiver vessel has a receiver door with a receiver door fluid seal.
 17. The method recited in claim 12 wherein the absorption media is a metallic wool. 